linux-kernel - Re: [PATCH] x86/microcode/AMD: Fix out-of-bounds on systems with CPU-less NUMA nodes

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Message-ID: <20250307164429.GCZ8sibd8HT8R7gfs9@fat_crate.local>
Date: Fri, 7 Mar 2025 17:44:29 +0100
From: Borislav Petkov <bp@...en8.de>
To: Dave Hansen <dave.hansen@...el.com>
Cc: Florent Revest <revest@...omium.org>, linux-kernel@...r.kernel.org,
	tglx@...utronix.de, mingo@...hat.com, dave.hansen@...ux.intel.com,
	x86@...nel.org, hpa@...or.com, stable@...r.kernel.org
Subject: Re: [PATCH] x86/microcode/AMD: Fix out-of-bounds on systems with
 CPU-less NUMA nodes

On Fri, Mar 07, 2025 at 08:32:20AM -0800, Dave Hansen wrote:
> On 3/7/25 07:58, Florent Revest wrote:
> > One thing I'm not entirely sure about is that
> > for_each_node_with_cpus() is implemented on top of
> > for_each_online_node(). This differs from the current code which uses
> > for_each_node(). I can't tell if iterating over offline nodes is a bug

You better not have offlined nodes when applying microcode. The path you're
landing in here has already hotplug disabled, tho.

> > or a feature of load_microcode_amd() so this would be an extra change
> > to the business logic which I can't really explain/justify.
> 
> Actually, the per-node caches seem to have gone away at some point too.
> Boris would know the history. This might need a a cleanup like Boris
> alluded to in 05e91e7211383. This might not even need a nid loop.

Nah, the cache is still there. For now...

for_each_node_with_cpus() should simply work unless I'm missing some other
angle...

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette